Parallel multi wafer axial spin clean processing using spin cassette inside movable process chamber

ABSTRACT

A system and method concurrently processes multiple wafers. A cassette structure includes multiple chucks and a drive spool for supporting and rotating the chucks. Each chuck holds a wafer in position while rotating. The cassette structure is loaded into a process chamber. Each chuck includes a self-locking mechanism that is activated by the centrifugal force generated from the rotation of the chuck. The self-locking mechanism centers and holds a wafer in position with respect to the chuck. A drive motor drives the drive spool, which causes the chucks to rotate. As the chucks are being rotated, a dispensing assembly delivers a processing chemical to the wafers.

TECHNICAL FIELD OF THE INVENTION

The present application relates generally to wafer clean processing and,more specifically, to a method and apparatus for cleaning multiplewafers in parallel using a single cassette and processing chamber.

BACKGROUND OF THE INVENTION

The concept of multi-wafer parallel processing is expensive to fabricateconsidering the complexity of the design. And there is a limited marketdemand due to limited processing steps required for single waferprocessing, resulting in a lack of return on investment (ROI)justification to pursue simultaneous multi-wafer cleaning. As such, noserious attempt has been made to create equipment for parallelprocessing of two or more wafers using a single cassette.

Now, because the shrinking geometries on processing chips require singlewafer processing at several processing steps, the idea of multi-waferprocessing with the efficiency of single wafer cleaning becomes relevantfor future cleaning equipment technology. The current throughput issuesare being addressed by increasing the fabrication floor space and thenumber of single wafer tools. Chamber stacking has also been done toreduce the tool footprint, but chambers are still isolated andthroughput issues still exist.

SUMMARY OF THE INVENTION

A system for processing multiple wafers is provided. The system includesa cassette structure and a chamber for loading the cassette structure.The cassette structure includes multiple chucks and a drive spool forsupporting and rotating the chucks. Each chuck, when rotating, holds awafer in position.

A method for cleaning two or more wafers in a single process chamber isprovided. The method includes loading multiple wafers onto a set ofchucks. Each wafer is placed on one of the chucks, and each chuck is atleast partially supported by a drive spool. The cassette structure isloaded into a chamber. The drive spool is rotated to simultaneouslyrotate the chucks. And each wafer is held in position for processingusing the rotation of the plurality of chucks.

An apparatus for processing multiple wafers is provided. The systemincludes a cassette structure that includes multiple chucks and a drivespool for supporting and rotating the chucks. Each chuck includes aself-locking mechanism to hold a wafer in position while rotating. Thesystem also includes a chamber into which the cassette structure isloaded.

An apparatus for securing a wafer is provided. The apparatus includes acircular plate and a self-locking mechanism. The circular plate includesa substantially planar top surface on which the wafer is placed. Theradius of the top surface is greater than a radius of the wafer. Theself-locking mechanism centers the wafer about an axis of rotation ofthe upper circular portion and holds the wafer according to acentrifugal force generated by a rotation of the circular plate.

Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, itmay be advantageous to set forth definitions of certain words andphrases used throughout this patent document: the terms “include” and“comprise,” as well as derivatives thereof, mean inclusion withoutlimitation; the term “or,” is inclusive, meaning and/or; the phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like; and theterm “controller” means any device, system or part thereof that controlsat least one operation, such a device may be implemented in hardware,firmware or software, or some combination of at least two of the same.It should be noted that the functionality associated with any particularcontroller may be centralized or distributed, whether locally orremotely. Although definitions for certain words and phrases areprovided throughout this patent document, those of ordinary skill in theart should understand that in many, if not most instances, suchdefinitions apply to prior, as well as future uses of such defined wordsand phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates a multi-wafer clean processing system according tothe present disclosure;

FIG. 2 illustrates a process cassette being loaded into a processchamber according to an embodiment of the present disclosure;

FIG. 3 illustrates a lateral view of a process cassette and a dispensingassembly according to an embodiment of the present disclosure;

FIG. 4A illustrates a top view of a floating chuck according to anembodiment of the present disclosure;

FIG. 4B illustrates a cross-sectional view of a floating chuck accordingto an embodiment of the present disclosure;

FIG. 4C illustrates an exploded cross-sectional view of a self-lockingmechanism according to an embodiment of the present disclosure; and

FIG. 5 illustrates a process for processing multiple wafers in parallelaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 5, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure may beimplemented in any suitably arranged wafer processing system.

FIG. 1 illustrates a multi-wafer clean processing system according tothe present disclosure. The multi-wafer clean processing system 100includes a process cassette 110, a process chamber 120, a drive motor130, and a nozzle dispense assembly 140. The multi-wafer cleanprocessing system 100 addresses the throughput limitation of currentsingle wafer cleaning tools by loading two or more wafers at a time.

According to an embodiment, the process cassette 110 allows parallelprocessing of two or more wafers using an axial spin rotation cleaningprocess. The process cassette, to be described in further detail withregard to FIG. 3, includes floating chucks that are driven by the drivemotor 130. The floating chucks are supported on periphery by a pluralityof rotating spools that are spindle-like structures, at least one ofwhich is coupled to the drive motor 130. Each of the floating chucksincludes a mechanism that self-locks a wafer in position using therotational speed of the floating chuck.

The process chamber 120, according to an embodiment, may be movedvertically to allow the loading and unloading of the stationary processcassette 110 into the multi-wafer clean processing system 100. Theprocess chamber 120 and/or the process cassette 110 may also be capableof horizontal motion and provide extra throughput. In an embodiment, theprocess chamber 120 may comprise a substantially cylindrical shape. Theprocess chamber 120, to be described in further detail with regard toFIG. 3, may also include exhaust/drain waffles to prevent backsplash ofchemical from the chamber walls to the lower level floating chucks.

The drive motor 130 may be coupled to one of the spools (e.g. a drivespool) of the process cassette 110. In an embodiment, the drive motor130 may rotate the drive spool using its single drive. Rotating thedrive spool may cause the floating chucks to rotate axially and, inturn, cause the other spools to rotate while supporting the floatingchucks. The centrifugal force of the rotating chucks will then cause theself-locking mechanism to hold the wafers in place.

The nozzle dispense assembly 140, to be described further with regard toFIG. 3, delivers a cleaning agent (e.g. cleaning chemical or liquefiedgas) to the wafers during the cleaning process. In an embodiment, thecleaning agent may be delivered from the top of the multi-wafer cleanprocessing system 100 to each wafer by a common swing system withscanning arms. A scanning arm that includes a separate line to a nozzlemay be provided to deliver the cleaning agent to each wafer, separately.

FIG. 2 illustrates a process cassette being loaded into a processchamber according to an embodiment of the present disclosure. Accordingto an embodiment, process chamber 120 is moved vertically to allowloading and unloading of process cassette 110, which may be stationary.That is, when process chamber 120 is lowered to expose the processcassette 110, wafers that need to be processed may be loaded into theprocess cassette 110. When loading is complete, process chamber 120 maybe raised to enclose the process cassette 110 for processing.

For embodiments in which the drive motor 130 is coupled to a bottomportion of the process chamber 120, a chamber motor coupling portion 225at the bottom portion of the process chamber 120, and a cassette motorcoupling portion 215 at a bottom portion of the process cassette 110 maybe provided. That is, when the process chamber 120 is raised to enclosethe multi-wafer clean processing system 100, the chamber motor couplingportion 225 is coupled to the cassette motor coupling portion 215 suchthat, during processing, the drive spool of the cassette is rotated bythe drive motor 130.

As already discussed, the process chamber 120 may also includeexhaust/drain waffles 228 to prevent backsplash of chemical from thechamber walls to the lower level floating chucks of the process cassette110. Each of the exhaust/drain waffles 228 line the interior wall of theprocess chamber 120 and extend from the interior wall diagonally towardthe top of the process chamber 120. As such, in embodiments in which theprocess chamber comprises a cylindrical shape, the exhaust/drain waffles228 resemble rings that are vertically spaced apart. The angle of theexhaust/drain waffles 228 from the horizontal axis are such that whenchemicals are applied from the nozzle to the wafer, the backsplash iscaught by the exhaust/drain waffles 228 and drained along the wall ofthe process chamber 120.

When processing is complete, process chamber 120 may be lowered again toallow the processed wafers (e.g. cleaned wafers) to be unloaded from theprocess cassette 110 before unprocessed wafers are loaded. When theunprocessed wafers are loaded into the process cassette 110, processchamber 120 may be raised to enclose the multi-wafer clean processingsystem 100 and repeat the processing of the newly loaded unprocessedwafers.

In an embodiment, two or more process cassettes 110 may be provided toallow the efficient loading and unloading of the cassette. For example,during processing of a first process cassette, a second process cassettemay be loaded with unprocessed wafers. When processing of the wafers inthe first cassette is completed, the process chamber 120 is lowered. Theprocess chamber 120 or the process cassettes may be capable ofhorizontal motion in such that the second process cassette may be placeddirectly above the process chamber 120. Then, the process chamber 120may be raised to enclose the second process cassette for processing.During processing with the second process cassette, the processed wafersin the first process cassette may be unloaded, and the next set ofunprocessed wafers may be loaded onto the first process cassette. Inanother embodiment, a third process cassette may be loaded withunprocessed wafers while the processed wafers in the first processcassette are unloaded. In essence, the number of process cassettes andthe sequence of loading and unloading wafers may be adjusted to optimizethe throughput of the multi-wafer clean processing system 100.

FIG. 3 illustrates a lateral view of a process cassette and a dispensingassembly according to an embodiment of the present disclosure. Processcassette 110 includes a plurality of spools. According to an embodiment,each spool may comprise a vertical spindle-like structure in whichgrooves or notches are spaced vertically apart to support an edge of afloating chuck 320. In the embodiment illustrated in FIG. 3, processcassette 110 comprises three spools 310 a-c that are positionedapproximately 120 degrees apart from the center of the horizontal plane.In an embodiment, each of the three spools include the same number ofnotches/grooves with corresponding notches/grooves at the same verticalposition such that the floating chucks 320 may lay substantially flatone a horizontal plane when supported by the spools 310 a-c.

In an embodiment, spool 310 a may be the drive spool. That is, thecassette motor coupling portion 215 may be associated with spool 310 a.When process chamber 120 is raised for processing, the cassette motorcoupling portion 215 of spool 310 a may be coupled to the chamber motorcoupling portion 225 such that the drive motor 130 may rotate spool 310a about its vertical axis to rotate the floating chucks 320 that arebeing supported by the spools. In some embodiments, each of the spools310 a-c may have a cassette motor coupling portion such that the spoolthat is lined up with the chamber motor coupling portion 225 may act asthe drive spool during processing.

The nozzle dispense assembly 140 may comprise a nozzle scan motor 330,at least one chemical line 340, a common swing system 350, and aplurality of nozzles 360. At least one chemical line 340 feeds theprocessing chemical, such as a cleaning agent (e.g. isopropyl alcohol,nitrogen gas, and such), to the nozzle dispense assembly 140. The commonswing system 350, which comprises a substantially vertical tube-likeshaft, is coupled to the nozzle scan motor 330. Each of the plurality ofnozzles 360 comprises an arm that extends laterally from the commonswing system 350. In an embodiment, each of the plurality of nozzles 360may correspond with a notch (or groove) of the spools 310 a-c to deliverthe processing chemical to the corresponding wafer. That is, each nozzle360 may extend laterally from the common swing system 350 to deliver theprocessing chemical on the top surface of the wafer that is securelypositioned on the corresponding floating chuck 320.

The nozzle scan motor 330 drives the common swing system 350 in anoscillating motion such that the dispense nozzles 360 rotate clockwiseand counter-clockwise about the vertical axis of the common swing system350 inside the wall of the process chamber 120 while the drive spool 310a rotates the floating chuck 320. The angle of oscillating rotation maybe determined based on the radius of the wafer or the floating chuck320. In another embodiment, the common swing system 350 may operatesimilarly to a crankshaft such that when the nozzle scan motor 330rotates the common swing system 350, the alternating nozzles 360 move intoward the center of the floating chuck 320 and back toward the wall ofthe process chamber 120 in an oscillating manner. In essence, the nozzledispense assembly 140 applies the processing chemical to the entire topsurface of each wafer and allows all the wafers to be processedconcurrently while the driving spool 310 a rotates all the floatingchucks in parallel.

FIGS. 4A-4C illustrate a floating chuck according to an embodiment ofthe present disclosure. FIG. 4A illustrates a top view of a floatingchuck according to an embodiment of the present disclosure. As can beseen, spools 310 a-c are positioned approximately 120 degrees apartabout the center of the floating chuck 320. Although the topcross-sectional view for notches of the spools 310 a-c resemble asubstantially circular shape, this is only meant for illustrativepurposes and is not intended to limit the scope of the disclosure. FIG.4B illustrates a cross-sectional view of a floating chuck according toan embodiment of the present disclosure.

Floating chuck 320 is a substantially circular structure that comprisesa lower portion 410, an upper portion 420, and a self-locking mechanismthat comprises a plurality of pin assemblies 440. As can be seen inFIGS. 4A and 4B, the lower and upper portions 410 and 420 of thefloating chuck 320 are substantially circular plates that are concentric(i.e. have a common center). In an embodiment, the lower portion 410comprises a substantially circular shape with a radius that extendslaterally such that the edge of the lower portion 410 rests on thenotches of the spools 310 a-c. The upper portion 420 may comprise asubstantially circular shape with a radius that has a value between theradius of a wafer 430 and the radius of the lower portion 410. That is,the lower portion 410 interacts with the spools 310 a-c and the upperportion 420 supports the wafer 430. Each pin assembly 440 in FIG. 4A isshown with dotted lines to represent that at least a portion of the pinassembly 440 may be located beneath the wafer 430 and/or beneath theupper portion 420 of the floating chuck 320. The dotted arrows on eachpin assembly 440 represent that at least a portion of the pin assembly440 may be rotated. This will be described further with respect to FIG.4C.

In FIG. 4C, an exploded cross-sectional view of a portion 450 of FIG. 4Billustrates one of the pin assemblies 440 of the self-locking mechanismaccording to an embodiment of the present disclosure. In essence, thepin assemblies 440 of the self-locking mechanism work together tosecurely hold the wafer 430 in position using a centrifugal force thatis generated when the floating chuck 320 is rotated.

In an embodiment, each pin assembly 440 may comprise a pin 442, amechanical bearing 444, and an eccentric weight 445. The pin 442 may befixed to a top surface of the mechanical bearing 44 such that the pin442 extends vertically (or upwards at an angle) near an edge of the topsurface of the mechanical bearing 444 that rotates about the verticalaxis 448. The mechanical bearing 448 may be fastened at or near an outeredge of the upper portion 420 such that the mechanical bearing 448 hasthe same thickness as the upper portion 420. In another embodiment,circular cavities may be provided at or near a radial distance from thecenter of the upper portion 420.

The eccentric weight 445 is located in a hollow portion of the bottomportion 410 of the floating chuck 320, and one end of the eccentricweight 445 is coupled to the bottom of the mechanical bearing 444, suchthat the center of mass of the eccentric weight 445 is laterally offsetfrom the vertical axis 448 (i.e. center of rotation of the mechanicalbearing 444). Therefore, the mechanical bearing 444 operates as a pivotfor the eccentric weight 445. Furthermore, the mechanical bearing 444 isconfigured such that, when the eccentric weight 445 turns about thevertical axis 448 (i.e. the pivot), the top surface of the mechanicalbearing 444 also rotates, causing the pin 442 to move in a circular pathabout the vertical axis 448. That is, when the eccentric weight 445turns about the pivot, the rotating motion is translated to the pin 442.In an alternate embodiment, the mechanical bearing 444 may be replacedby any other mechanism that can be used as a pivot for the eccentricweight. For example, the mechanical bearing 444 may include a hollowcenter portion. In an embodiment, the pin 442 may be directly fixed tothe eccentric weight 445, which may be configured include a pivot thatextends through the upper portion 420.

The self-locking mechanism, according to an embodiment, operates asfollows. When the floating chuck 320 is resting (i.e. not beingrotated), the pin 442 of each pin assembly 440 is located in a restingposition such that the radial distance between the center of the upperportion 420 and the pin 442 is greater than the radius of the wafer 430.In an embodiment, a spring mechanism may be provided to hold the pin 442in its resting position. When the floating chuck 320 is rotated by thedrive motor 130, the centrifugal force generated by the rotation of thefloating chuck 320 causes the eccentric weight 445, which is coupled tothe mechanical bearing 444, to pivot about the vertical axis 448. Theturning of the eccentric weight 445 about the vertical axis 448 (i.e.the pivot) of each pin assembly 440 causes the pin 442 to move in acircular motion about the vertical axis 448 until the pin 442 abutsagainst the edge of the wafer 430 and cannot move further.

As such, when the floating chuck 320 rotates, the pin 442 of each pinassembly 440 abuts against the edge of the wafer 430, causing the wafer430 to be centered with respect to the rotation of the floating chuck320 and securely held in place. In essence, the force of theself-locking mechanism is based at least partially on the rotationalspeed of the floating chuck 320. Therefore, as rotation of the floatingchuck 320 slows to a halt, the pins 442 of the self-locking mechanismrelease the wafer 430. Consequently, the self-locking mechanism, asdescribed, can be used to center and secure hold wafers with differentdimensions based on the range of motion for the pin assembly 440.Therefore, it may not be necessary to modify a floating chuck based onwafer size.

In FIG. 4C, pin 442 of the pin assembly 440 shown to have a bottomportion that is substantially conical (or prism-like) and a flat topportion such that, when the floating chuck 320 rotates, the wafer 430 iselevated as the pins 442 move inwards in a circular path about thevertical axis 448 after making contact with the wafer 430 until the topsurface of the wafer 430 abuts the flat top portion of the pin 442. Inother embodiments, pin 442 may comprise any other shape (e.g. a straightpin or a hook) that is appropriate for securely holding the wafer 430 inposition during rotation of the floating chuck 320.

Furthermore, FIG. 4A illustrates a self-locking mechanism that comprisessix pin assemblies 440 that are spaced apart at substantially equalangles from each other and at an equal distance with respect to thecenter of the upper portion 420 of the floating chuck 320. However, thisis merely for illustrative purposes and is not meant to limit the scopeof the present disclosure. In other embodiments, the self-lockingmechanism of the floating chuck 320 may comprise three or more pinassemblies 440. In some embodiments, the pin assemblies 440 may not bespaced at substantially equal angles from each other with respect to thecenter of the floating chuck 320.

In the embodiment illustrated in FIGS. 4A and 4C, one end of theeccentric weight 445 is coupled to the mechanical bearing 444 such that,when in a resting position, the majority of the eccentric weight 445extends toward the center of the floating chuck 320. In FIGS. 4A and 4C,the eccentric weight 445 is illustrated as having an elliptical (oroval) shape comprising a flat top surface and a flat bottom surface.However, this is merely for illustrative purposes and is not intended tolimit the shape or orientation of the eccentric weight 445. For example,the eccentric weight 445 may be coupled to the mechanical bearing 444such that, when in a resting position, the majority of the eccentricweight 445 extends away from the center of the floating chuck 320. Thatis, the eccentric weight 445 may comprise any shape and may be orientedin any way as long as the center of mass of the eccentric weight 445 islaterally offset with respect to the vertical axis 448 such that therotation of the floating chuck 320 causes the eccentric weight 445 torotate about the vertical axis 448, thereby causing the pin 442 of eachpin assembly 440 to move toward the center of the wafer 430.

In an embodiment, the lower portion 410 may be a single circular platecomprising a plurality of hollow portions, where each hollow portionaccommodates the rotation of an eccentric weight 445. In anotherembodiment, the lower portion 410 may comprise an inner circular plateportion and an outer circular ring, such that the gap between the innercircular plate portion and the outer circular ring provides sufficientspace for the rotation of the eccentric weights 445. In yet anotherembodiment, the lower portion 410 may be a single ring-shaped plate witha hollow center to accommodate the eccentric weights 445. In someembodiments, the hollow portions of the lower portion 410 of eachfloating chuck 320 may be enclosed to prevent the eccentric weight 445from being exposed.

FIG. 5 illustrates a process 500 for processing multiple wafers inparallel according to an embodiment of the present disclosure. In block510, wafers (e.g. wafers 430) are loaded onto a process cassette (e.g.process cassette 110). That is, each wafer 430 is loaded onto the upperportion 420 of a floating chuck 320 such that the pins 442 of the pinassemblies surround the wafer 430. Block 510 assumes that the processcassette 110 is not currently enclosed by the process chamber 120 (e.g.the process chamber 120 has been lowered to expose the process cassette110, or the process chamber 120 is currently being used to processanother process cassette). In another embodiment, the wafers 430 mayfirst be loaded onto the floating chucks 320, and the floating chucksmay then subsequently be loaded onto the spools to form the processcassette 110.

In block 520, the process cassette 110 is loaded into the processchamber 120. In an embodiment, the process chamber 120 is raised toenclose the process cassette 110. In another embodiment, the processcassette is lowered into the process chamber 120. When loaded, processcassette 110 is positioned such that the drive spool 310 a is coupled tothe drive motor 130. In an embodiment, the chamber motor couplingportion 225 is coupled to the cassette motor coupling portion 215.

In block 530, the floating chucks 320 are rotated. That is, the drivemotor 130 rotates the drive spool 310 a which then causes the floatingchucks 320 in the process cassette 110 to rotate. Rotating the floatingchucks 320 subsequently causes the other spools 310 b and 310 c to alsorotate by frictional force. Meanwhile, the centrifugal force generatedby the rotation of the floating chucks 320 activates the self-lockingmechanism. As discussed with regard to FIGS. 4A-4C, a self-lockingmechanism comprising pin assemblies 440 is provided for each floatingchuck 320 to securely hold the wafer 430 at the center with respect tothe axis of rotation of the floating chuck 320. In an embodiment thatcomprises multiple process cassettes, another process cassette may beprepared by loading the next batch of unprocessed wafers. Furthermore, apreviously processed cassette may be unloaded. Alternatively, if themulti-wafer clean processing system 100 includes two process cassettesand a first process cassette is currently loaded into the processchamber 120, processed wafers are unloaded from the exposed processcassette, and unprocessed wafers are subsequently loaded onto theexposed process cassette.

In block 540, the wafers in the process cassette 110 may be processedconcurrently. The nozzle scan motor also drives the common swing system350 to cause the nozzles 360 to oscillate. At least one chemical line340 draws a processing chemical through the common swing system 350 tothe nozzles 360, which deliver the processing chemical to the wafers430. The backsplash of the processing chemical is collected by theplurality of exhaust/drain waffles 228. In the embodiment that comprisesmultiple process cassettes, one or more exposed process cassettes areprepared for processing, as described with regard to block 530.

After the multi-wafer clean processing system 100 has completedprocessing wafers 430, the process cassette 110 is unloaded from theprocess chamber 120 (block 550). In an embodiment, the process chamber120 is lowered to expose the process cassette 110. In anotherembodiment, the process cassette 110 is raised from the process chamber120. In an embodiment in which the multi-wafer clean processing system100 includes a single process cassette, when the process cassette 110 isunloaded, the processed wafers 430 may be unloaded from the floatingchucks 320 of the process cassette 110, and the process may return toblock 510 to load the next batch of unprocessed wafers onto the processcassette 110.

Alternatively, in embodiments in which the multi-wafer clean processingsystem 100 comprises two or more process cassettes, the process returnsto block 520 and loads the next process cassette into the processchamber 120. The processed wafers 430 may then be unloaded from processcassette 110 concurrently while the multi-wafer clean process resumes inblock 530.

Although the present disclosure has been described with an exemplaryembodiment, various changes and modifications may be suggested to oneskilled in the art. It is intended that the present disclosure encompasssuch changes and modifications as fall within the scope of the appendedclaims.

1. A system for concurrently processing multiple wafers, the systemcomprising: a cassette structure comprising multiple chucks and a drivespool for supporting and rotating the chucks, each chuck configured tohold a wafer in position while rotating; and a chamber for loading thecassette structure.
 2. The system of claim 1, wherein the multiplechucks in the cassette structure are supported in parallel by the drivespool, such that multiple wafers are processed in parallel.
 3. Thesystem of claim 1, wherein each chuck comprises at least one pinassembly configured to lock a wafer in position using a centrifugalforce generated when the chucks in the cassette structure are rotated.4. The system of claim 3, wherein each chuck further comprises: an upperportion comprising a plurality of circular holes substantially normal tothe upper portion, each circular hole located at a radial distance fromthe center of rotation of the chuck; and a lower portion comprising atleast one cavity that overlaps at least one circular hole of the upperportion, wherein each pin assembly comprises a pin that extends aboveone circular hole of the upper portion and an eccentric weight pivotallyheld in the cavity of the lower portion and configured to turn about theone circular hole.
 5. The system of claim 4, wherein when the eccentricweight turns within the cavity about the center of the one circular holeof the upper portion, the pin moves in a circular path about the centerof the one circular hole of the upper portion.
 6. The system of claim 1,further comprising: a motor coupling interface configured to couple thedrive spool to a motor.
 7. The system of claim 1, further comprising: adispensing assembly configured to concurrently deliver chemicals to thewafers.
 8. A method for processing multiple wafers, the methodcomprising: loading a plurality of wafers onto a plurality of chucks,each wafer placed on one of a plurality of chucks at least partiallysupported by a drive spool; loading the cassette structure into achamber; rotating the drive spool to simultaneously rotate the pluralityof chucks; and holding each of the plurality of wafers in position forprocessing using the rotation of the plurality of chucks.
 9. The methodof claim 8, wherein the plurality of chucks are at least partiallysupported in parallel by the drive spool.
 10. The method of claim 8,wherein holding each of the plurality of wafers to be held in positionfor processing comprises: locking a wafer in position using acentrifugal force generated by the rotation of the plurality of chucks.11. The method of claim 10, wherein locking the wafer in position usingthe centrifugal force generated by the rotation of the plurality ofchucks comprises: providing a number of pin assemblies that arerotatably attached at a radial distance about the center of rotation ofthe chuck, each pin assembly comprising a pin extending above a circularhole of the upper portion and an eccentric weight pivotally held in acavity of the lower portion, wherein the eccentric weight turns aboutthe circular hole.
 12. The method of claim 11, wherein the centrifugalforce generated by the rotation of the plurality of chucks causes theeccentric weight to turn about the circular hole, and wherein turningthe eccentric weight causes the pin to move in a circular path about thecenter of the circular hole.
 13. The method of claim 8, wherein thedrive spool is rotated by a motor.
 14. The method of claim 8, furthercomprising simultaneously dispensing chemicals to each of the pluralityof wafers as the plurality of chucks are rotated.
 15. An apparatus forprocessing multiple wafers, the apparatus comprising: a cassettestructure comprising a plurality of chucks and a drive spool forsupporting and rotating the chucks, each chuck comprising a self-lockingmechanism to hold a wafer in position while rotating; and a cylindricalchamber into which the cassette structure is loaded.
 16. The apparatusof claim 15, wherein the chucks in the cassette structure are at leastpartially supported in parallel by the drive spool, such that multiplewafers are processed in parallel.
 17. The apparatus of claim 15, whereinthe self-locking mechanism in each chuck comprises a number of pinassemblies positioned about the center of rotation of the chuck andconfigured to lock a wafer in position using a centrifugal forcegenerated when the chucks in the cassette structure are rotated.
 18. Theapparatus of claim 17, wherein each chuck comprises: an upper portioncomprising a plurality of circular holes substantially normal to theupper portion, each circular hole located at a radial distance from thecenter of rotation of the chuck, the pin assemblies pivotally disposedat the circular holes; and a lower portion comprising a cavity thatoverlaps at least one circular hole of the upper portion when the upperportion is mounted onto the lower portion, and wherein each pin assemblyin the self-locking mechanism comprises a mechanical bearing disposed inone circular hole of the upper portion, a pin that extends above themechanical bearing, and an eccentric weight pivotally attached to abottom portion of the mechanical bearing in the cavity of the lowerportion and configured to turn about the mechanical bearing.
 19. Theapparatus of claim 18, wherein the eccentric weight turns within thecavity about the center of rotation of the mechanical bearing and causesthe pin to move in a circular pattern about the center of rotation ofthe mechanical bearing.
 20. The apparatus of claim 15, furthercomprising: a dispensing assembly configured to concurrently deliverchemicals to the wafers; and a plurality of drain ducts along the sidewall of the cylindrical chamber to prevent backsplash of the chemicalsto lower chucks in the cylindrical chamber.
 21. An apparatus forsecuring a wafer, the apparatus comprising: a circular plate comprisinga substantially planar top surface on which the wafer is placed, whereina radius of the top surface is greater than a radius of the wafer; and aself-locking mechanism configured to center the wafer about an axis ofrotation of the upper circular portion and hold the wafer according to acentrifugal force generated by a rotation of the circular plate.
 22. Theapparatus of claim 21, wherein the self-locking mechanism comprises aplurality of pin assemblies located, each pin assembly comprising a pinthat extends above the circular plate and located at a radial distancefrom the axis of rotation of the circular plate.
 23. The apparatus ofclaim 22, wherein each pin assembly further comprises: a mechanicalbearing disposed in the circular plate and configured to serve as apivot for the pin assembly, the pin extending upward from the mechanicalbearing at a radial distance from the center of the mechanical bearing;and an eccentric weight pivotally attached to a bottom portion of themechanical bearing and configured to turn about the axis of rotation ofthe mechanical bearing.
 24. The apparatus of claim 23, wherein thecentrifugal force generated by the rotation of the circular plate causesthe eccentric weight to turn about the axis of rotation of themechanical bearing.
 25. The apparatus of claim 24, wherein the pinassembly is configured to move the pin in a circular path about the axisof rotation of the mechanical bearing when the eccentric weight turns.